The invention pertains to trailer platforms used to transport heavy equipment to remote operational sites, capable of being lowered to ground level for operation of the equipment.
There are numerous applications, in various industries, in which it is necessary to transport very heavy equipment by road to remote operational sites. In the oil industry, for example, it is often necessary to transport large drilling mud tanks, and associated pump equipment, to remote drilling sites. Such equipment typically has a weight of the order of 20,000 lbs., or more, with the tank empty.
It is important that during transport of such equipment the transporting vehicle provide ample over-the-road clearance. This is particularly true in oil field operations, since the last portion of the journey must often be made over very rough, uneven terrain.
Once the equipment has arrived at the operational site, it is often necessary or at least desirable that the equipment can be operated at ground level. Operating characteristics of the equipment may require operation at ground level. For example, a large oil industry drilling mud tank may be too heavy when full to be supported above ground on a trailer platform. The most convenient general approach to this problem is through use of a trailer platform bearing the equipment, which platform is capable of being lowered to ground level at the operational site.
Where very heavy equipment is involved, as in the abovedescribed oil industry application, it is obviously essential that the means used to lower the trailer to ground level afford great stability during the lowering process, to minimize the risk that the entire rig may capsize, with possibly very damaging consequences for equipment and personnel.
The patent of Couse (U.S. Pat. No. 2,751,234) discloses a truck trailer having hydraulic jacks capable of lowering the trailer to ground level. FIGS. 1-4, ref. Nos. 15-21; Col 1, lines 41-49. The trailer is equipped with a removable truck dolly, which, when attached to the trailer, is attached in a fixed position. FIGS. 1-3, ref. No. 5; Col 1, lines 28-29, 47; Col 2, line 72--Col 3, line 3; FIGS. 8, 9, 11-18; Col 2, lines 28-30; Col 3, lines 17-70.
The patent of Gostomski (U.S. Pat. No. 3,567,271) discloses a camper unit having hydraulic cylinders capable of lowering the camper to ground level. Col 1, lines 12-18, 48-50; Col 2, lines 46-55; Col 5, lines 18-31; FIG. 1, ref. Nos. 36, 42.
The patent of Hulse (U.S. Pat. No. 4,273,347) discloses a truck trailer having a removable truck dolly having parallel rails which slide with tracks on the bottom of the trailer. FIG. 2, ref. Nos. 10, 12, 16, 18; Col 1, lines 10-12, 60-61; Col 2, lines 53-55. The dolly may be secured to the trailer at any of several fixed positions by the use of a pin passing through corresponding openings in one of the rails and one of the tracks. Col 1, line 61-63; FIG. 4, ref. Nos. 16, 18, 24. The patent indicates that such slidable dollies locked with pins had previously been known in the art. Col 1, lines 10-19.
The patent of Wisdom (U.S. Pat. No. 3,894,747) discloses a method and apparatus which may be used to lower a trailer bed to ground level. Col 1, lines 5-10. This is accomplished by a hydraulic lift mechanism of quite different form from that of the present invention. Col 2, line 38--Col 3, line 43; FIGS. 2, 5, ref. No. 26. The patent discloses that hydraulic cylinders have been mounted around the perimeters of trailer beds to "raise or lower the bed as necessary to remove the wheel assembly and subsequently place the trailer bed on the ground." Col 1, lines 21-26.
The patent of James (U.S. Pat. No. 3,419,169) discloses a hydraulically powered folding gooseneck trailer, with a hydraulic cylinder at the juncture of the trailer bed and trailer hitch platform, usable either to raise the hitch platform relative to the trailer bed, or to raise both the hitch platform and trailer bed together. Col 4, lines 27-50; FIGS. 1, 4, ref. No. 30.
The patent of Richey (U.S. Pat. No. 3,497,232) discloses a drop bed trailer of quite different form from that of the present invention, which does not involve a hydraulic system.
The patent of Selby (U.S. Pat. No. 3,734,529) discloses a trailer frame designed for elongated loads, such as mobile homes, not involving hydraulics, and of very different form from the trailer of the present invention.
The patent of McGaughan (U.S. Pat. No. 1,989,940) discloses a portable service station having a removable truck dolly. Page 2, Col 1, lines 14-22; FIG. 4. No hydraulic system is described, but the patent states that the truck dolly can be removed if the station is raised by suitable jacks. p. 2, Col 1, lines 10-12.
The patent of Wallace (U.S. Pat. No. 2,576,907) discloses a hydraulic apparatus, of quite different form from the present invention, employing hydraulic cylinders for lifting vehicles from below, which apparatus is movably mounted in tracks in a floor. Col 2, line 20--Col 3, line 57; FIG. 1.
The patent of Donaldson (U.S. Pat. No. 2,294,110) discloses a boatwheel chassy in which the wheel can be swung up to facilitate disconnecting it from the boat, and is not believed to be directly relevant to applicant's invention.
Where a trailer with a removable truck dolly is used to transport very heavy equipment, as in oil industry applications described above, the truck dolly itself is quite heavy, often weighing of the order of 4,500 pounds. Thus, in trailers of the form shown in Couse or Hulse several men may be required to remove or reattach the truck dolly. Also, when the dolly is completely removed to lower the trailer to ground level, and the equipment is to be used at a remote location for an extended period of time, there is the problem that the truck dolly could be stolen.
Applicant is not aware of any hydraulically operated trailer having a beneficial feature of applicant's invention, namely a truck dolly which is moved in or out from under the trailer by the hydraulic system when the trailer is to be raised or lowered, without manual labor, which dolly pivots upward in an arc about a junction at the rear of the trailer, remaining attached when the trailer is operated at ground level.
Applicant is aware of a hydraulic jack assembly, (hereinafter "Gallagher assembly") not described in any patent known to applicant, which has, according to applicant's present information, been in public use in the United States for several years, which is in one respect similar to the individual hydraulic jack assemblies used in the preferred embodiment of applicant's invention. In the Gallagher assembly, as in applicant's assembly, telescoping square tubes are used in conjunction with a hydraulic cylinder. In the Gallagher assembly, the hydraulic cylinder is inside the telescoping square tubes, whereas in applicant's trailer platform the hydraulic cylinder and the telescoping square tubes are parallel, with neither inside the other.
The patents referred to above are all of the patents which applicant learned of from a search carried out at the Patent and Trademark Office, which search was ordered with reference to the present invention.